"There are very serious questions about whether our government has forgotten the lessons of 9/11," Grassley said during a speech on the Senate floor.

"Lack of information sharing and failure to see real warning signs are probably things that no bill will fix," he said. "What has to change is the culture [and] ... it requires true leadership."

Grassley is the latest Republican to rail against perceived failures by the intelligence and law enforcement communities in the aftermath of the Boston bombings.

Republicans said reports that Tamerlan Tsarnaev, one of the two brothers suspected in the Boston attacks, was put on a terrorism watch list at the request of the CIA a year before the bombings was proof of a broken intelligence system.

“The FBI and the CIA have great people, but you know [we are] going backwards in national security,” he added.

On Friday, Grassley reiterated those concerns, questioning whether the intelligence sharing problems that plagued the CIA and the FBI in the run-up to the 9/11 attacks led to Tsarnaev slipping through the agencies' fingers.

"Our government was reportedly warned on multiple occasions that one of these brothers had become a radical jihadist," Grassley said.

"Do we still have agencies failing to follow up, failing to share information, and failing to connect the dots?" he asked.

Russian intelligence officials separately warned the FBI and CIA about Tsarnaev’s 2011 trip to Russia, where he may have reached out to militant Islamic groups in Dagestan.

Tsarnaev died after a shootout with federal agents and local police last Friday. His younger brother, Dzhokhar Tsarnaev, has been charged with using a weapon of mass destruction in the Boston attack, which killed three people and injured more than 200

But once the FBI made contact with Russian intelligence about their concerns over Tsarnaev’s 2011 trip, “all the intelligence agencies should have been notified,” Frederick Fleitz, a former CIA official, told The Hill on Thursday.

“Someone [must have] dropped the ball” during the FBI’s investigation to force Moscow to go to the CIA with its concerns, he added.

The problem, however, is much bigger than just figuring out how warning signs about the elder Tsarnaev were missed by American intelligence and law enforcement, according to the Iowa Republican.

"This is about much more than who dropped the ball," Grassley said. "It is about learning from mistakes, and doing a better job next time."